Continuous metal casting method and apparatus

ABSTRACT

In accordance with the invention, molten metal under pressure passes continuously through a mold to form a partially solidified casting with a solid shell and a molten metal. Before the pressure of the molten core ruptures the solid shell, the casting is advanced through a chamber and submerged in a liquid coolant in this camber. The liquid coolant continues the solidification of the casting and, at the same time, pressure is applied externally to the casting through the liquid coolant, preventing the pressure of the molten core from rupturing the solid shell. The casting is maintained submerged in the liquid coolant and under pressure until the solid shell is thick enough to prevent outbreak of the molten core in the absence of said pressure.

United States Patent Fromson CONTINUOUS METAL CASTING METHOD AND APPARATUS Howard A. Fromson, Rogues Ridge Road, Weston, Conn. 06880 May 7, 1970 [72] Inventor:

Filed:

Appl. No.:

Related U.S. Application Data [60] Continuation-impart of Ser. No. 829,921, June 3, 1969, Pat. No. 3,570,587, which is a division of Ser.

No. 596,292, Nov. 22, 1966, Pat. No. 3,468,361.

[5 6] References Cited UNITED STATES PATENTS 3,468,361 Fromson ..164/89 3,570,587 3/1971 Fromson ..l64/283 Primary Examiner-J. Spencer Overholser Assistant E.raminer.lohn E. Roethel Attorney-Ralph D. Dinklage, Arnold Sprung and John E.

Lynch [57] ABSTRACT In accordance with the invention, molten metal under pressure passes continuously through a mold to form a partially solidified casting with a solid shell and a molten metal. Before the pressure of the molten core ruptures the solid shell, the casting is advanced through a chamber and submerged in a liquid coolant in this camber. The liquid coolant continues the solidification of the casting and, at the same time, pressure is applied externally to the casting through the liquid coolant, preventing the pressure of the molten core from rupturing the solid shell. The casting is maintained submerged in the liquid coolant and under pressure until the solid shell is thick enough to prevent outbreak of the molten core in the absence of said pressure.

14 Claims, 3 Drawing Figures PATENTEnAPRzs I972 3,658,117 SHEET 10F 2 FIG. 1

INVENTOR. HOWARD A. FROM SON BY F. 2 65 Mae.

ATTOR NEYS CONTINUOUS METAL CASTING METHOD AND APPARATUS The application herein is a continuation-in-part of application Ser. No. 829,921 filed June 3, 1969, now US. Pat. No. 3,570,587 which in turn is a division of application Ser. No. 596,292, now U.S. Pat. No. 3,468,361.

The present invention relates to the art of continuously casting molten metal.

In the continuous casting of molten metal such as steel, the metal is continuously fed under pressure through a liquidcooled mold made of metal having high conductivity, such as copper or copper alloy. The metal in contact with the mold walls partially solidifies, forming a solid shell filled with a molten metal core. This casting is continuously pulled through the mold and, as further cooling progresses, the molten core gradually solidifies.

If the casting is withdrawn from the mold at too fast a rate, the shell will be so thin, that the pressure of the molten metal in the core will break through the shell. It has, therefore, been necessary to move the metal through the mold at a sufficiently slow rate, to assure the formation of a solid shell therein, thick enough to prevent the shell from being ruptured by the pressure ofthe molten metal core, as the partially solidified casting passes beyond the confining protection of the mold walls. These conditions slow down production, so that the full potential of continuous casting operation is not realized.

One object of the present invention is to provide a new and improved process and apparatus for continuously casting metal by simple economic means and at a rate higher than that possible by known operations.

In accordance with the present invention, molten metal is introduced continuously under pressure through a mold having a bore with cooling walls. The molten metal is fed through the mold at a rate, slow enough to produce a partially solidified casting therein consisting of a solid outer shell and a core of molten metal, but fast enough so that if the casting so formed were exposed to the atmospheric pressure as it emerges from the mold, the molten metal under pressure in the core would break out through the outside shell. To permit efficient operation at this comparatively fast rate, the casting partially formed in the mold as described, is advanced from the mold as it is continuously formed therein, and directly into a tank containing a bath of liquid coolant, having a melting point below that of the metal being cast, such as a molten salt, as for example, barium chloride. The static pressure exerted by the liquid coolant on the partially solidified casting is such, as to counteract the core pressure in said casting and thereby to prevent rupturing of the solid shell due to said core pressure. While the casting is advancing, it is maintained in said liquid coolant under external pressure until the casting is sufficiently solidified in said coolant to prevent outbreak of the molten core through the solid shell, in the absence of coolant pressure. The length of the liquid coolant tank along the course of the casting therethrough is substantial, to give the casting sufficient time, notwithstanding its comparatively high rate of advancement, to solidify to a condition stable enough to prevent outbreak of the liquid core through the solid shell, as the casting emerges from the tank into the atmosphere. The operation described permits the casting to be formed at a rate not possible in the absence of a liquid coolant.

The static pressure exerted by a body of liquid coolant on the partially solidified casting therein, where the upper surface ofthe liquid coolant is exposed to the atmosphere is equal substantially to the depth of the casting multiplied by the weight per unit volume of the liquid coolant. Where the tank is fully open to the atmosphere at the top, the amount of liquid coolant is substantial.

Another object of the present invention is to provide a new and improved process and apparatus for continuously casting metal sufficiently and economically with the use ofa comparatively small amount ofliquid coolant.

In accordance with certain features of the present invention, a main chamber is provided for a body of liquid coolant creating on the partially solidified casting advancing therethrough, a certain static pressure, which is a function of the height of the coolant in said chamber above the casting and additional pressure is applied to the immersed casting through said body of liquid coolant by means requiring little or no additional liquid coolant. The means for creating the additional pressure may, in one embodiment of the invention, take the form of a column of liquid coolant posed on only a portion of the top of the body of liquid coolant in said chamber, so that the pressure exerted by the liquid coolant on the casting is equal to the combined height of the liquid coolant in the chamber and in the column. This pressure is the same as the pressure exerted by a body of liquid coolant having this combined height and uniform in horizontal cross section to this height. By the use ofa column of liquid coolant in the manner described, the same pressure is applied but with less liquid coolant.

In accordance with another embodiment of the invention, the means for creating additional pressure on the body of liquid coolant in the main chamber takes the form of controlled gas pressure applied to the entire top of the body of liquid coolant or applied to a portion ofthis top. For example, it could be applied directly to the surface of the liquid coolant in the chamber, so that the pressure exerted on the casting in the liquid coolant would be that due to the height of the liquid coolant in said chamber plus that due to the gas pressure, or a column of liquid coolant can be posed on a portion of the body ofliquid coolant in the chamber, as described above, and the gas pressure applied directly to the top surface of said column, in which case, the pressure applied to the partially solidified casting would be that due to the combined height of the body of liquid coolant in the main chamber and of the column of liquid coolant and the gas pressure applied to said column of liquid coolant.

As an additional feature of the present invention, the main chamber for the liquid coolant is cylindrical in shape, so that the hydrostatic pressure exerted by the liquid coolant on the casting therein due solely to the coolant in said chamber is comparatively large in relation to the amount of coolant in said chamber.

Other objects, features and advantages of the present inven tion are apparent from the following description and from an inspection of the accompanying drawings, in which FIG. 1 is a vertical section through an apparatus taken on line 1-1 of FIG. 2, and showing in full lines, one structural embodiment of the present invention for carrying out a method, constituting one embodiment of the process aspects of the present invention, and showing in combined full lines and in dot and dash lines, an apparatus constituting another structural embodiment of the present invention for carrying out a method constituting another embodiment of the process aspects of the present invention,

FIG. 2 is a vertical section of the apparatus taken on line 2 of FIG. 1, and

FIG. 3 is a vertical section through a portion of the apparatus showing in greater detail the mold part of the ap paratus.

Referring to the drawings, the casting apparatus of the present invention comprises a tundish or reservoir 10 for retaining molten metal 11, such as steel, at a substantially constant level and lined with a refractory wall 12 to maintain the metal molten therein. This reservoir 10 is supplied with molten metal from a ladle (not shown), and has an outlet 13, leading into the inlet end of an open-ended, liquid-cooled casting mold 14. The outlet end of this mold 14 connects into one end of a tank 16, shown cylindrical and horizontal, and containing a liquid coolant 17. The liquid coolant 17 is of any suitable material having a melting point substantially below that of the metal being cast, and desirably solid at room temperature. A suitable liquid coolant would be barium chloride.

The tank 16 is housed in a furnace l8 lined with a refractory wall 19 and has a valved drain pipe 20 connected to the bottom of the tank and slanting downwardly and forwardly of said furnace for easy accessibility. Burners 21 supported on the furnace wall 19, heat the tank 16 at least at the beginning of operations, to fuse the coolant 17 into molten condition, and this coolant is maintained at a temperature substantially below the melting temperature of the metal being cast during operations to assure effective cooling of this casting. The furnace 18 has a flue or chimney 18a connected thereto.

The mold 14 has a substantially horizontal casting bore 22 of any desirable cross-sectional shape; this cross-sectional shape, may be round, as shown, to produce, for example, an ingot of continuous length. The mold 14 has a peripheral wall 23 of metal, having high heat conductivity, such as copper. This mold wall 23 is liquid-cooled, and for that purpose, is provided with a jacket 24 around said mold wall having an inlet 25 and an outlet 26 for cooling liquid, such as water. A baffle plate 27 in the form of an annulus is positioned in the jacket 24 between its inlet 25 and outlet 26 to prevent direct by-pass of the water between said inlet and said outlet. This baffle plate 27 extends to a sleeve 28 radially spaced from the mold wall 23 and provided with circular series of openings 29 at the ends to permit flow of cooling water into and out of the annular space between said mold wall and said sleeve.

The part of the apparatus between the reservoir 10 and the inlet end of the casting mold 14 is fully heat-insulated by refractory material, so that the metal in this part of the apparatus is in fully molten condition. The level of the molten metal 11 in the reservoir 10 is high enough, so that the metal enters the mold 14 at substantial pressure. As this metal passes through the water-cooled mold 14, it begins to solidify at the periphery of the mold to form a partially solidified casting 30 having a thin solid shell 31 and a core 32 of molten metal at substantial pressure, as shown. In this partially solidified form, the external shape of the casting 30 as formed in the mold 14, will be retained by the casting as it enters the tank 16, and the static pressure exerted by the liquid coolant 17 in said tank on the outside of the casting, will counteract the pressure of the molten metal in the core 32 and will prevent thereby distortion of said casting and outbreak of said core metal through the shell 31. The partially solidified casting 30 is advanced continuously substantially horizontally and centrally through the tank 16, so as to be surrounded on all sides by uniform amounts of liquid coolant 17 in the tank, and is supported against sagging in said central position by horizontal support bars 33 in said tank, secured to the wall thereof. The casting 30 may be advanced through the tank 16 by any suitable means, as for example, pulling rollers (not shown) beyond the outlet end of the tank.

As the casting 30 is advanced through the liquid coolant 17 in the tank 16, it is cooled by the coolant and the thickness of the solid shell 31 becomes progressively greater. The horizontal length of the body of liquid coolant 17 in contact with the casting is, at least such, as to cause the casting to be sufficiently solidified before emerging from said body of liquid coolant, to prevent outbreak of the molten core 32, when the casting emerges into the atmosphere.

The casting in the stabilized condition described, emerges from the body of molten coolant 17, passes through a watercooled seal 35 closing off the outlet end of the tank 16, and is further cooled by water-sprays 36 into completely solidified condition, as the casting emerges into the atmosphere. The completely solidified casting may be cut into pieces of desired length.

To reduce the cost of the system of the present invention and the cost of its operation, the system is designed to obtain the maximum static pressure of the liquid coolant l7 and a maximum length of casting travel through said coolant with a minimum amount of coolant. For this purpose, the tank 16 serving as the principal chamber for the liquid coolant 17 is cylindrical in shape, as described. The static pressure exerted by the liquid coolant 17 on the casting 30 advancing therethrough, due solely to the coolant filling the cylindrical tank 16, will be the same as that exerted by a liquid coolant on a casting centrally advancing along a tank having a square transverse vertical cross-section of a width and height corresponding to the internal diameter of the cylindrical tank 16, notwithstanding the fact that the amount of coolant filling said cylindrical tank is substantially less than that filling the square tank.

Also, means are provided for exerting on only a portion of the top of the body of liquid coolant 17 in the tank 16, static pressure requiring little or no additional liquid coolant. In the embodiment of this feature shown solely in full lines in the drawings, there is connected to the top of the tank 16 near its midsection an upstanding columnar pipe 40 of small horizontal cross-sectional area compared with the horizontal diametrical cross-sectional area of the tank. This pipe 40 is shown cylindrical in shape and, communicates with the interior of the tank 16, to serve as a restricted off-shoot of said tank and as a means for filling the tank. The pipe 40 is shown slanting upwardly and forwardly of the furnace 18 to render the upper end of said pipe easily accessible for filling. The pipe 40 contains liquid coolant 17 to the level a according to the additional hydrostatic pressure desired to be externally applied to the liquid coolant in the tank 16 and is open at the top to the atmosphere in the full-line embodiment of the invention shown in FIG. 2. The column of liquid coolant 17 in the pipe 40 not only affords the additional hydrostatic pressure described with minimum of additional liquid coolant, but also serves to maintain the tank 16 filled with coolant.

With the arrangement described and shown in full lines, and the columnar pipe 40 open to the atmosphere, the static pressure exerted by the liquid coolant 17 on the casting 30 will be the height h (FIG. 2), multiplied by the weight of the liquid coolant per unit volume.

In another embodiment of the present invention, instead of exposing the body of liquid coolant 17 to the atmosphere, gas pressure, such as air pressure, is applied to the surface of the liquid coolant 17. This expedient for obtaining the additional pressure desired, not only has the advantage of attaining this additional pressure with little or no additional liquid coolant 17, but has the advantage of permitting quick and selective control of the static pressure applied to the casting 30 through the liquid coolant.

The embodiment of the invention in which gas pressure is applied to the liquid coolant 17 to attain additional static pressure is shown in full lines and in dot and dash lines in FIG. 2, and is shown in conjunction with the use of the columnar pipe 40, although as far as certain aspects of the invention are concerned, this columnar pipe can be eliminated, and the gas pressure applied directly to the surface of the body of the liquid coolant 17 in the tank 16.

As shown in full and dot and dash lines, the top of the columnar pipe 40 has a sealing cover 41 with a pipe connection 42 connected to a suitable gas pressure pump 43. With this arrangement, the static pressure applied to the casting 30 in the tank 16 by the liquid coolant 17 is equal to the hydrostatic pressure due to the height h of liquid coolant 17 plus the gas pressure applied to the top surface of the liquid coolant.

What is claimed is:

1. A method of continuously casting molten metal comprising continuously introducing molten metal under pressure into a mold having a bore with cooling walls to produce a partially solidified casting comprising a solid shell surrounding a molten core, continuously advancing said casting as it is formed and while in partially solidified condition from said mold directly into contact with a body of liquid coolant at a rate to cause a substantial length of said casting to be immersed in said liquid coolant while in said partially solidified condition, said body of liquid coolant applying to the casting hydrostatic pressure which is a function of the height of the surface of said body of liquid coolant above the casting in said liquid coolant, applying to the top of said body of liquid coolant substantial additional pressure, which does not require for the purpose of attaining this additional pressure as much liquid coolant as would be required by an upward extension of the entire body of liquid coolant, the pressures acting on the periphery of said partially solidified casting through said liquid coolant being sufficiently high to counteract the core pressure in said casting and thereby to prevent rupturing of said solid shell due to said core pressure, maintaining the advancing casting in said liquid coolant under counteracting pressure until the casting has reached a sufficiently solidified state in said liquid coolant to prevent outbreak of the molten core in the absence of said counteracting pressure, and continuously discharging the casting from said body of liquid coolant after attaining said solidified state.

2. A method as described in claim 1, wherein said additional pressure is applied by a column of liquid coolant posed on only a portion of the top of said body ofliquid coolant and upstanding therefrom.

3. A method as described in claim 2, wherein said body of liquid coolant is retained in a closed tank except for a pipe extending upwardly from the top of said tank and holding said column ofliquid coolant.

4. A method as described in claim 3, wherein said tank is cylindrical in shape and extends substantially horizontal, and said casting is advanced substantially horizontally substantially through the center of said tank.

5. A method as described in claim 1, wherein said additional pressure is applied by gas pressure to at least a portion of the top surface of said body of liquid coolant.

6. A method as described in claim 2, wherein gas pressure is applied to the top surface of said column ofliquid coolant.

7. A method of continuously casting molten metal comprising continuously introducing molten metal under pressure into a mold having a bore with cooling walls to produce a partially solidified casting comprising a solid shell surrounding a molten core, continuously advancing said casting as it is formed and while in partially solidified condition from said mold directly into contact with a body ofliquid coolant retained in a horizontal cylindrical tank at a rate to cause a substantial length of said casting to be immersed in said liquid coolant while in said partially solidified condition, applying to the periphery of the partially solidified casting through the liquid coolant, pressure sufficiently high to counteract the core pressure in said casting and thereby to prevent rupturing of said solid shell due to said core pressure, and said casting being advanced through said tank substantially horizontally along the longitudinal axis of said tank, maintaining the advancing casting in said liquid coolant in said tank under said counteracting pressure until the casting has reached a sufficiently solidified state in said liquid coolant to prevent outbreak of the molten core in the absence of said counteracting pressure, and continuously discharging the casting from said tank after attaining said solidified state.

8. An apparatus for continuously casting molten metal comprising a mold open at both ends to permit continuous transit of a metal therethrough, means for continuously feeding molten metal under pressure through said mold, means for cooling the walls of said mold sufficiently to cause the metal passing therethrough to be formed into a partially solidified casting having a solid outer shell and a core of molten metal, means forming a chamber containing a body of liquid coolant and located in position to receive the casting as it leaves said mold, to cause the casting to come into contact with the liquid coolant in said chamber and to be peripherally subjected to the hydrostatic pressure exerted by the liquid coolant in said chamber, means for continuously advancing the casting through the body of liquid coolant in said chamber, means for creating additional pressure over the body of liquid coolant in said chamber aside from atmospheric pressure, requiring less liquid coolant than would be required if the entire body of liquid coolant were upwardly extended sufficiently to create this additional pressure, the pressure created by the conjoint action of said body of liquid coolant and said means for creating additional pressure being sufficient to counteract the core pressure in said casting and thereby to prevent rupturing of said solid shell due to said core pressure, means for maintaining the advancing casting in said body of liquid coolant under counteracting pressure until the casting has reached a sufficiently solidified state in said body of liquid coolant to prevent outbreak of the molten core in the absence of said counteracting pressure, and means for continuously discharging the casting from said body of liquid coolant after attaining said solidified state.

9. An apparatus as described in claim 8, said means for attaining additional pressure comprising means forming a column of liquid coolant posed on only a portion of the top of said body of liquid coolant and upstanding therefrom.

10. An apparatus as described in claim 8, said chamber forming means comprising a horizontal cylindrical tank, said column forming means comprising a pipe extending upwardly from the top of said tank and forming an ofi-shoot of said tank, said casting advancing means advancing said casting substantially horizontally and substantially through the center of said tank.

11. An apparatus as described in claim 8, said means for attaining additional pressure comprising means for creating gas pressure and applying it to said casting through said body of liquid coolant.

12. An apparatus as described in claim 9, said means for attaining additional pressure also comprising means for creating gas pressure and applying it to the surface of said column.

13. An apparatus for continuously casting molten metal comprising a mold open at both ends to permit continuous transit of a metal therethrough, means for continuously feeding molten metal under pressure through said mold, means for cooling the walls of said mold sufficiently to cause the metal passing therethrough to be formed into a partially solidified casting having a solid outer shell and a core of molten metal, a horizontal cylindrical tank containing a body of liquid coolant and located in position to receive the casting for movement in said tank along the longitudinal axis thereof as the casting leaves said mold, to cause the casting to come into contact with the liquid coolant in said tank and to be peripherally subjected to the hydrostatic pressure exerted by the liquid coolant in said tank, means for creating additional pressure over the body of liquid coolant in said chamber aside from atmospheric pressure, the pressure created by the conjoint action of said body of liquid coolant and said means for creating additional pressure being sufficient to counteract the core pressure in said casting and thereby to prevent rupturing of said solid shell due to said core pressure.

14. An apparatus for continuously casting comprising a mold having a substantially horizontal bore and open at both ends to permit continuous transit of a metal therethrough in a substantially horizontal direction, means for continuously feeding molten metal under pressure through said mold, means for cooling the walls of said mold sufficiently to cause the metal passing therethrough to be formed into a partially solidified casting having a solid shell and a core of molten metal, means forming a horizontal cylindrical tank containing a body of liquid coolant and located in position to cause the partially solidified casting to enter said tank substantially horizontally and substantially upon leaving said mold and to traverse said tank submerged in said body of liquid coolant, means for continuously advancing the casting substantially horizontally through said tank submerged in said body of liquid coolant, means for subjecting said casting while submerged in said liquid coolant to such peripheral pressure through said body of liquid coolant as to prevent rupturing of said solid shell due to said core pressure, and including said body of liquid coolant, said tank being long enough and said advancing means advancing the casting through said tank at such a rate as to cause said casting eventually to be sufficiently solidified while submerged in said body of liquid coolant to prevent outbreak of the molten core in the absence of said pressure.

a: a: s x e 

2. A method as described in claim 1, wherein said additional pressure is applied by a column of liquid coolant posed on only a portion of the top of said body of liquid coolant and upstanding therefrom.
 3. A method as described in claim 2, wherein said body of liquid coolant is retained in a closed tank except for a pipe extending upwardly from the top of said tank and holding said column of liquid coolant.
 4. A method as described in claim 3, wherein said tank is cylindrical in shape and extends substantially horizontal, and said casting is advanced substantially horizontally substantially through the center of said tank.
 5. A method as described in claim 1, wherein said additional pressure is applied by gas pressure to at least a portion of the top surface of said body of liquid coolant.
 6. A method as described in claim 2, wherein gas pressure is applied to the top surface of said column of liquid coolant.
 7. A method of continuously casting molten metal comprising continuously introducing molten metal under pressure into a mold having a bore with cooling walls to produce a partially solidified casting comprising a solid shell surrounding a molten core, continuously advancing said casting as it is formed and while in partially solidified condition from said mold directly into contact with a body of liquid coolant retained in a horizontal cylindrical tank at a rate to cause a substantial length of said casting to be immersed in said liquid coolant while in said partially solidified condition, applying to the periphery of the partially solidified casting through the liquid coolant, pressure sufficiently high to counteract the core pressure in said casting and thereby to prevent rupturing of said solid shell due to said core pressure, and said casting being advanced through said tank substantially horizontally along the longitudinal axis of said tank, maintaining the advancing casting in said liquid coolant in said tank under said counteracting pressure until the casting has reached a sufficiently solidified state in said liquid coolant to prevent outbreak of the molten core in the absence of said counteracting pressure, and continuously discharging the casting from said tank after attaining said solidified state.
 8. An apparatus for continuously casting molten metal comprising a mold open at both ends to permit continuous transit of a metal therethrough, means for continuously feeding molten metal under pressure through said mold, means for cooling the walls of said mold sufficiently to cause the metal passing therethrough to be formed into a partially solidified casting having a solid outer shell and a core of molten metal, means forming a chamber containing a body of liquid coolant and located in position to receive the casting as it leaves said mold, to cause the casting to come into contact with the liquid coolant in said chamber and to be peripherally subjected to the hydrostatic pressure exerted by the liquid coolant in said chamber, means for continuously advancing the casting through the body of liquid coolant in said chamber, means for creating additional pressure over the body of liquid coolant in said chamber aside from atmospheric pressure, requiring less liquid coolant than would be required if the entire body of liquid coolant were upwardly extended sufficiently to create this additional pressure, the pressure created by the conjoint action of said body of liquid coolant and said means for creating additional pressure being sufficient to counteract the core pressure in said casting and thereby to prevent rupturing of said solid shell due to said core pressure, means for maintaining the advancing casting in said body of liquid coolant under counteracting pressure until the casting has reached a sufficiently solidified state in said body of liquid coolant to prevent outbreak of the molten core in the absence of said counteracting pressure, and means for continuously discharging the casting from said body of liquid coolant after attaining said solidified state.
 9. An apparatus as described in claim 8, said means for attaining additional pressure comprising means forming a column of liquid coolant posed on only a portion of the top of said body of liquid coolant and upstanding therefrom.
 10. An apparatus as described in claim 8, said chamber forming means comprising a horizontal cylindrical tank, said column forming means comprising a pipe extending upwardly from the top of said tank and forming an off-shoot of said tank, said casting advancing means advancing said casting substantially horizontally and substantially through the center of said tank.
 11. An apparatus as described in claim 8, said means for attaining additional pressure comprising means for creating gas pressure and applying it to said casting through said body of liquid coolant.
 12. An apparatus as described in claim 9, said means for attaining additional pressure also comprising means for creating gas pressure and applying it to the surface of said column.
 13. An apparatus for continuoUsly casting molten metal comprising a mold open at both ends to permit continuous transit of a metal therethrough, means for continuously feeding molten metal under pressure through said mold, means for cooling the walls of said mold sufficiently to cause the metal passing therethrough to be formed into a partially solidified casting having a solid outer shell and a core of molten metal, a horizontal cylindrical tank containing a body of liquid coolant and located in position to receive the casting for movement in said tank along the longitudinal axis thereof as the casting leaves said mold, to cause the casting to come into contact with the liquid coolant in said tank and to be peripherally subjected to the hydrostatic pressure exerted by the liquid coolant in said tank, means for creating additional pressure over the body of liquid coolant in said chamber aside from atmospheric pressure, the pressure created by the conjoint action of said body of liquid coolant and said means for creating additional pressure being sufficient to counteract the core pressure in said casting and thereby to prevent rupturing of said solid shell due to said core pressure.
 14. An apparatus for continuously casting comprising a mold having a substantially horizontal bore and open at both ends to permit continuous transit of a metal therethrough in a substantially horizontal direction, means for continuously feeding molten metal under pressure through said mold, means for cooling the walls of said mold sufficiently to cause the metal passing therethrough to be formed into a partially solidified casting having a solid shell and a core of molten metal, means forming a horizontal cylindrical tank containing a body of liquid coolant and located in position to cause the partially solidified casting to enter said tank substantially horizontally and substantially upon leaving said mold and to traverse said tank submerged in said body of liquid coolant, means for continuously advancing the casting substantially horizontally through said tank submerged in said body of liquid coolant, means for subjecting said casting while submerged in said liquid coolant to such peripheral pressure through said body of liquid coolant as to prevent rupturing of said solid shell due to said core pressure, and including said body of liquid coolant, said tank being long enough and said advancing means advancing the casting through said tank at such a rate as to cause said casting eventually to be sufficiently solidified while submerged in said body of liquid coolant to prevent outbreak of the molten core in the absence of said pressure. 